In ocular imaging, proper alignment of the optical axes of the subject's eye and the imaging optics is a prerequisite to avoid unwanted reflections quality ocular image acquisition. However, there are 12 degrees of freedom (6 on the part of the subject's eye, and 6 on the part of the imaging system, making this a nontrivial task. Traditional approaches to achieving alignment rely on an operator manually aligning the axes of the imaging device to that of the subject's eye, or robotic (automated) alignment of the axes of the imaging system to that of the subject's eye. Both trained operators and robotic alignment add cost and complexity to the imaging workflow. For example, manual handheld fundus cameras require the operator to manually position a camera in three-dimensional space along 6 degrees of freedom, and often require an integrated screen to view the eye, while the head of the subject is partially restrained leaving 3 degrees of freedom, for a total of 9 degrees of freedom. Traditional manual desk-mounted fundus cameras require the operator to manually steer the camera with a joystick, 6 degrees of freedom, while the subject's eye is restrained with a chinrest and headband as well as fixation, leaving 6 degrees of freedom in total. Automated or semi-automated fundus cameras require complex motors, additional cameras and sensors, and built-in image processing to drive the automated alignment along 6 degrees of freedom, thereby adding significant cost, and also restrain the subject's eye using chinrest, headband and fixation.
The human eye, however, is the endpoint for a highly versatile cybernetic system that can align the optical axis of the eye with respect to external objects along 6 degrees of freedom. Because there is a need in the art for an alignment system with reduced cost, complexity, and ease of operation, it is attractive to use the natural alignment of the human body.